The present invention relates to an arrangement for fitting of valve sacks on a filling pipe or filling pipes of a packaging machine. It deals for example with side fold valve sacks which are closed at their opposite sides with closing seams extending transversely to the longitudinal edges, and in which the valve is provided under a closing seam in one longitudinal side wall.
Arrangements of the above mentioned general type are known in the art. One of such arrangements is disclosed, for example in the PCT-Application No. WO/81/01543. In this document a spreading device which is composed of two semishells moves in this arrangement into the easily opened valve to pull the valve up so wide that it is fittable on the filling pipe. For pulling up the valve, one shell is turnable about a horizontal axis. After the valve has been pulled up the sack in the valve region is engaged by turnable guiding flaps. The shape of the guiding flaps corresponds to the contour of the pulled up valve, so that the valve cannot close. Then, the sack is fitted on the filling pipe by a respectively controlled movement of the guiding flaps. This arrangement is suitable exclusively for cross bottom valve sacks which are formed of several paper layers and have a relatively high rigidity.
The rigidity of flat sacks, side fold sacks is not comparable with that of the cross bottom sacks, especially in the case when the sacks are produced from a synthetic plastic foil. With the sacks in question it is not possible to maintain the shape of the pulled up valve by outwardly engaging guiding flaps. Moreover, because of the arrangement of the valve in the side wall under a closing seam, it is practically impossible to introduce the tool in the region of the valve. A further disadvantage of the above described known arrangement is that after the pulling up of the valve, a transfer is performed on the means by which the sack is fitted on the filling pipe.